I just want to know that in order to build app in Android platform for epub reader, what might be the time span to get the ereader done, considering we are welcome guys to android platform where we have taken android course, and team of 3 members.
Kindly advise what could be our time span and hurdle we might expect.
Thanks in advance.

Wouldn't that depend on how quickly you produce valid code and the complexity/quantity of the features you plan to offer??

I would recommend, and request, that if/when you do create an app that you make sure it is in compliance with ePub standards... Copying or licensing someone else's software that isn't in compliance just prolongs the pain we are dealing with now!